The invention relates to test chambers for subjecting an object to varying environmental conditions, such as varying temperature and humidity. More particularly, the invention relates to the circulation of conditioned air in such test chambers.
In prior test chambers, a heater in the circulation system is used to heat the air and a refrigeration coil in the system is used to cool the air. If the refrigeration coil remains in the path of air circulation when hot air is being circulated, the heated air picks up moisture from frost and ice on the refrigeration coil. Since the object being tested is at a lower temperature than the moisture containing heated air, undesirable condensation on the object will result as the heated air passes over it.
Another problem with prior test chambers is the time lag between shifting from a hot condition to a cold condition, and vice versa. This occurs because it is often necessary to heat or cool the entire test chamber before the temperature of the object being tested is sufficiently changed. Accordingly, a great deal of time is wasted.